| Pili bifurcati is an uncommon transitory hair shaft dysplasia with characteristic of segmental duplication of the hair shaft. Patients generally present with diffuse alopecia. Hypopigmentation can be observed. This anomaly of the hair shaft occurs in normal hair, pili canaliculi, or monilethrix and has been associated with the mosaic trisomy 8 syndrome, pseudomonilethrix type II or protein deficiency states. It can also be secondary to ulcerative colitis and extensive bowel resection. Caused by a transient duplication of the papilla's tip during the anagen phase, leading to the transitory production a two complete shafts, in the same follicular matrix, that emerge through a single pilary canal. When the two papilla tips fuse, both parallel branches form a single shaft again. When the transient duplication of the papilla tip occurs repetitively during the anagen phase, a series of bifurcation-fusion can be observed along the shaft. This situation is called pili multi-bifurcati. As a duplicated papilla tip can split again, a doubly bifurcated shaft may be observed: pili bi-bifurcati. |
